This makes it so that if CEGUI is compiled with gcc or clang, the gcc-specific compiler extensions will be enabled.Some projects would prefer not to enable these extensions, because, some of them conflict with the official standard, and others,might not be supported by other compilers. If people want to statically link CEGUI into their project and it only compiles withthese extensions, though, then they might be forced to change compilers to something that supports these extensions.

Does CEGUI actually use these extensions?If not, can I request or suggest that we make it `std=c++11` instead of `gnu++11 ` above?